In the tobacco industry, packing lines are normally used comprising a cartoning machine and a boxing machine, and along which packets of cigarettes are packed in two successive steps: a first step in which groups of normally ten packets are formed and enclosed inside a container to form so-called “cartons” on the cartoning machine; and a second step, in which the boxing machine forms a succession of groups of cartons, which are stacked to form a succession of multilayer groups, each of which is enclosed inside a respective box of cardboard or similar.
In packing machines of the above type, the cartoning and boxing machines are normally two separate machines, and the cartoning machine is connected to an input of the boxing machine by a carton group forming device, and by a pocket conveyor which feeds the cartons to the group forming device and extends through a carton quality control station and a carton reject station.
One of the drawbacks typical of known packing lines of the above type is that, when a carton is rejected at the reject station, a gap, i.e. an empty pocket, is formed along the conveyor connecting the cartoning machine to the boxing machine, and an incomplete group of cartons is formed, and subsequently rejected, on the group forming device on the boxing machine.
One solution employed to eliminate this drawback is to form, for example, along the connecting conveyor, a portion along which the cartons are pushed forward to fill any gaps. Alternatively, the cartons in the incomplete groups rejected by the boxing machine are fed back to the transfer conveyor immediately downstream from the reject station, and used to replace the rejected cartons.
Both the above known solutions involve using completely separate cartoning and boxing machines, a group forming device, and a relatively long, complex connecting conveyor.